Mishnah Berura, OC 8 (4) [10] says that the brocho on the Talis Godol is “lehisataif b*e*tzitis” and not as I see in the all my siddurim “lehisataif b*a*tzitis”. Are there many cases where what we do differs from the psak of the Mishnah Berura?

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And on a serious note, yes there are. Are you looking for a complete list of minhagim that are different? You will likely find lots of shuls have lots of different minhagim (let alone differences between the US and Israel and other places). I think you need to make your question more specific.
– Double AA♦Feb 4 '12 at 23:58

I believe the Mishna Berura even says not to say "Berich Shemeh" while most Ashkenazim still say it. I think if there is a Minhag that existed before the MB Ashkenazim might keep it (most of the time).
– Hacham GabrielFeb 5 '12 at 0:39

I've closed this question for the reason @DoubleAA has mentioned: "Are you looking for a complete list of minhagim that are different? You will likely find lots of shuls have lots of different minhagim (let alone differences between the US and Israel and other places). I think you need to make your question more specific." Or, in the words of the stock close reason: "This question is... vague,... overly broad,... and cannot be reasonably answered in its current form." If you wish to edit it to something reopenable, by all means do so; ping me with @msh210, and I'll be glad to reopen it.
– msh210♦Feb 5 '12 at 3:51